The present invention relates to sound reproduction but particularly to a plurality of speakers arranged in a divergent pattern to approximate a hemisphere in order to disperse sound equally in all directions.
Prior art has taken many forms in an effort to reproduce faithfully and to direct sound waves successfully to the listener where ever he may be in the listening area and to eliminate dead spots or areas of sound wave cancelation. From basic driver and horn combinations to cabinets with multiple drivers, special crossover networks and tuned ports with baffled internal structures the designer has attempted to create an infinite acoustic baffle around the speaker driver elements in order to extend frequency band width and to reduce distortion to a minimum. The introduction of the accoustic suspended speaker system in which the speaker is sealed in a cabinet without ports has proved to be superior to the ported types in bandwidth but is somewhat less efficient. All of the afore mentioned systems reproduce sound as a wave front which radiates from the speaker face and must be directed toward the listener. This directional effect can lead to wave front cancelations or dead spots in the listening area caused by reflections from walls and furniture.
Two speakers placed back to back in a sealed container and excited in phase as shown by manger in U.S. Pat. No. 4,268,719 create an infinite baffle which is in the form of a plane parallel to and located between the two speakers. The distribution of sound from this combination more closely resembles an omnidirectional wave pattern which is less subject to reflection problems. Taking this approach further, more speaker elements may be included into different patterns such as those described by glassco in U.S. Pat. No. 4,673,057 in which a number of similar speakers are arranged so that each maintains a common angle of divergence with its adjacent speakers. It is apparent that if the number of speakers continued to increase in this system eventualy a sphere would be formed which would have nearly perfect omnidirectional radiation qualities. In an effort to produce a speaker system which has the maximum frequency response and best omnidirectional pattern one is forced to use as big a speaker as possible for the low frequency response and to add tweeter units to extend the upper frequency response and to use as many speakers in the design as is economical. The tradeoffs all considered, the dodecahedron seems to be the closest to the desired shape. However, a system of this shape using twelve standard eight inch woofers and twelve small tweeters weighs in at about one hundred pounds. This is a considerable weight to hang from a ceiling and is an awkward form to transport from place to place. Use of such a speaker system in a car or van would be impossible or at least impractical and two are required for stereo sound. Bisecting the dodecahedron on its equatorial plane as described by glassco to produce a stereo system limits its installation in a listening room to the middle of the room or to the middle of the ceiling which is not always possible.